Television reproducing method



Dec. 31, 1940' K. SCHLESINGER I 2,227,004

TELEVISION REPRODUCING METHOD Filed Jan. 22, 1936 Sheets-Sheet l w 2 73Y F} inlay/0K mym- Dec. 31 1940. K. SCHLESINGER TELEVISION REPRODUCINGMETHOD Fild Jan'.

22, 1956 2 Sheets-Sheet 2 Jnrenfon" Patented Dec. 31, 1940 1 r 2,227,004

UNITED STATES PATENT OFFICE TELEVISION REPRODUGING METHOD KurtSchlesinger, Berlin, Germany, assignor, by

mesne assignments, to Loewe Radio, Inc., a corporation of New YorkApplication January 22, 1936, Serial No. 60,296 r In Germany January 26,1935 2 Claims. (01. 178-73) In numerous instances in the television artit quite well corresponds with unequal spacing of the is necessary toconvert rectangular image areas image points. In practice it is to bededuced from into trapezoidal image areas, for example in the this thateven line spacing in the object plane case of all cathode ray tubes inwhich the image corresponds with uneven spacing in the image 5 isprojected on to an intercepting plate provided plane. This leads tostrong distortions of the 5 within the tube and disposed obliquely tothe axis television image, and in numerous methods, for

of the tube, and also in the case of transmitters example in therepetition method for the purpose operating with a spiral-aperture disc(Nipkow of avoiding flickering effect, even to incapability disc), thesectional area of which is always a of performing the imagetransmission, as in the trapezium bounded by tworadii. It has alreadylatter case the upper and'lower halves of the image been shown inearlier application Ser. No. 46,126 possess difierent scales and do notfit, therefore in what manner this problem of the trapezoidal oneagainst the other.

distortion may be accomplished by inclination of Closer investigation,however, shows that the the plane of the object and the plane of theimage described error in scale, which will be referred to when employinga lens of short focal distance. In in the following as scale error,.varies greatly in 5 the latter application, however, there has beenextent dependent on the angle at which the imagedescribed merely theaccomplishment of the producing rays fall on the image plane 3. Fortrapezoidal form. No mention was made on the example in Fig. 1 the samerectangular object area other hand of the manner in which upon the disisdisposed on one occasion between the points tortion of the area adistortion of the scale occurs 0, d, e (4) and on another occasionbetween the 20 in the transverse or longitudinal direction. points a, b,c (5). In both cases there are derived The novel features whichI-believe to be charfrom the rectangular areas 4 and 5 trapezoidalacteristic for my invention are set forth with areas 4 and 5', whichresult between correspondparticularity in the appended claims. Myinvening image points c'e (4) and a'c' (5) retion, however, both as toits organization and spectively. In the case of 4-4 the centre of 25method of operation together with further objects the image a. of theoriginal 4 develops laterally of and advantages thereof may be bestunderstood the middle position do of the image 4'. The scale byreference to the following description taken in error in this case isvery large. 0n the other connection with the accompanying drawings, inhand in the case of 5-5 the middle of the reprowhich in Fig. 1 there isillustrated in what manduction level a c is met exactly at b. The scale30 ner the error is occurring the disturbing effect of error, therefore,in this case is very small. It is which shall be removed according tothe present to be recognised from this: invention, Figs. 2a and 2b showthe manner in The smallest scale error is obtained in the case which therecognitions take efiect in the assemof a trapezoidal reproductionaccording to Fig. 1

bly of a television transmission system having a in that range ofpositionof object and image in 3 Nipkow disc. In Fig. 20. there is shownan arwhich the image-producing rays, taken through rangement with largescale error, while in Fig. 2b the centre-point of the lens, impingealmost verthere is illustrated the optical arrangement actically on theimage surface. Whereas in the case cording to the invention, of normalreproducing optical systems the lenses Fig. 3 shows the interceptingsurface of an are always so disposed that their plane is situated 40ikonoscope. as far as possible vertically to the producing bun- Fig. 1shows a lens I, which converts an object die of rays, as the aperturecapable of being atplane with the track 2 into an image plane withtained is then at a maximum, the lens in the case the track 3. Allrectangular areas having vertical of a reproducing apparatus serving toproduce edges situated in the plane 2 appear in the image trapezoidaldistortions is so disposed in accord- 45 plane 3 with trapezoidaldistortion. In the object ance with the invention that the rays fallobliqueplane the points a-f are spaced equal distances ly thereon,whilst the image intercepting plane is apart. They correspond with thepenetration situated vertically to the ys e relative points of the linesof a television image, which is angles between the planes of the O jec es and 0 situated vertically to the plane of the paper in image a ot e ecd t y, and 1 0 the dethe plane 2. Their reproduction points are to be re of r p l di or i n verned by the found on the track of the image plane3 by drawangle in 1 remains P a y var ableing the middle-point rays.They are designated 2 O S t e n er in wh c these reco a,'-f, It, i t brecognised from th drawing tions take effect in the assembly of atelevision that the equidistant spacing of the object pointstransmission sy m v n a N pkow disc. In

Fig. 2a there is shown an arrangement with large scale error. The lampcase 6 together with the film guding rollers l and the lens I belongs tothe casing 8 of the film projector, and in the arrangement according toFig. 2:]. must, therefore, be disposed inclinedly to the foot 9 by meansof a rotary joint I0. The middle-point ray I2 meets the Nipkowdisc II,which replaces the image plane 3 in Fig. 1, at an inclined angle, andthe lens I at right-angles. This arrangement, despite good control ofthe intensity of the light due to the favourable position of the lens I,is incapable of use for television purposes because the decomposition ofthe lines is accompanied by a considerable scale error.

The optical arrangement according to the invention is illustrated inFig; 2b. The same differs from Fig. 2a by the fact that this time themiddlepoint ray I2 impinges on the image plane, i. e., the disc I I,vertically. The lens I and the film I must accordingly be inclinedlydisposed in relation to this middle-point ray, whereby the difierencesin direction between the optical planes I, I and II do not vary inrelation to Fig. 2a. This arrangement operates practically without scaleerror, and offers from the point of view of operation the advantagesthat (l) the adjustment of the trapezoidal distortion may take place bydifferent inclination of the planes of film and lens, i. e., small andreadily manipulated structures, whereas in Fig. 2a this can only beadjusted by inclination of the entire machine casing, and that (2) themachine Band lamp case 6 may remain in horizontal disposal.

It must be specifically remarked that the image-producing rays shown inthe drawings, for example the middle-point rays, are in no way identicalwith the rays which do in point of fact cause the technicalreproduction. The requirements laid down in the application as regardsthe disposal of the constructional rays of the geometric reproductionare fulfilled by correct mutual adjustment of film lens and plane of theimage. Independently thereof the bundle of rays proceeding from the lamp5 may now be disposed in space as desired. In practice this bundle withcertainty only be disposed in such fashion of the lighting rayscertainly coincides in the majority of cases as regards their directionwith the middle-point ray of the reproducing construction in the mannerillustrated diagrammatically in Figs. 2a and 2b.

In Fig. 3 the intercepting surface of an ikonoscope is designated I3,whereby the problem exists of reproducing optically without scale errorthe trapezium I4, which is projected thereon by a cathode ray withconstant deflecting potential. According to the invention, themiddle-point of the lens must be disposed on the perpendicular line I2provided at the centre of the intercepting plate I3, and an adjustableinclination in relation to this axis I2 imparted to the lens I and to amatt plate I5. On to the matt plate I5, which may also be a mirror or atangible air image, there is projected in the manner known per se bymeans of a reproducing lens I6 an image of the remote object. I5 and I6may also be related parts of a reproducing camera.

I claim:

1. In a television system, means to produce a planar optical image, aplanar light responsive image receiving area angularly positionedrelative to the plane of the optical image, means for scanning the imagein the plane of the image receiving area, and an optical means forfocussing the optical image upon the image receiving area,

said optical means having its main axis so located relative to the imagereceiving area that the light in the plane of the bisector of the anglebetween the planar optical image and the image receiving area, whereby asubstantially rectangular optical image is converted into asubstantially trapezoidal image on the image receiving area and thevariance in length of the shorter and longer parallel sides of thetrapezoid so formed are proportional to variances in length in thescanning pattern at the plane of the image receiving area.

2. The system claimed in claim 1 wherein the planar light responsiveimage receiving area comprises a mosaic electrode structure supportedwithin a cathode ray tube and wherein the scanning means comprises anelectron beam.

KURT SCHLESINGER.

